The present invention relates to an image reading device, and more particularly, to an image reading device to be used in a facsimile, an image scanner, and the like.
An image reading device is adapted to read image information by arranging light recipient elements such as photosensors in an array so as to read an image by dividing it into minute picture elements and by scanning the array of light recipient elements along the image surface. In order to read image information correctly, a light emitting means is necessary to irradiate a sufficient amount of light onto the image surface. In the conventional image reading device, light emitting means in the form of emitting elements such as LEDs are arranged in an array like the light recipient elements of the device so that the light irradiated from these light emitting elements is reflected by the image surface so as to be incident upon the light recipient elements.
FIG. 10 shows a general construction of a conventional image reading device, in which an end surface of a light waveguide 3 whose light guiding core portion 3a is covered by a cladding portion 3b confronts the light receiving surface of a photosensor 1 installed on a circuit board 2, and the waveguide 3 is arranged downward in the vertical direction with the other end surface thereof being positioned adjacent to the image surface of an original 4, and the light waveguide 3 is installed on a base stand 6 constituting the main body of the image reading device.
To one side of the light waveguide 3, there is provided an LED 5 installed on a separate circuit board 5a from the circuit board 2. The LED 5 is installed near the tip end of the light waveguide 3 in a downward angled direction so that the light emitted from the LED 5 efficiently irradiates the image surface immediately below the end surface of the light waveguide 3, and the light reflected by the image surface of the original 4 is introduced excellently into the light waveguide 3 arranged in the vertical direction. In order to arrange the LED 5 in the angled direction, the LED 5 and the circuit board 5a are fastened on an inclined surface of the base stand 6. The circuit board 2 carrying the photosensor 1 is fastened on the upper surface of the base stand 6 with a small screw 2a, with a cover 6a being installed above the base stand 6 so as to cover the photosensor 1 and circuit board 2.
It is to be noted here that a large number of photosensors 1 and LEDs 5 are arranged in parallel in an array in a direction perpendicular to the plane of the drawing so that the image reading throughout the entire length of the original is possible by reading the image in a transverse linear direction.
However, in such a conventional image reading device as described above, the LEDs 5 corresponding to the photosensors 1 constituting picture elements throughout the entire length of the image reading range are required to be arranged in parallel, so that there has been a problem that the manufacture of such an LED array is troublesome and high in cost. Furthermore, when the image reading range becomes long, the control circuit for the LED 5 becomes long, which makes the manufacturing cost of the circuit board 5a expensive. Further, a problem also exists with the arrangement of the photosensors 1 as light recipient elements.
Furthermore, in the conventional image reading device, since the light of the LEDs 5 is arranged to be incident directly upon the image surface, there has been such problems that in order to apply light properly, the installation position and posture of the LEDs are restricted and are troublesome.